1. Field of the Invention
The present invention relates to a technology for driving a stepping motor for a sheet processing device or the like.
2. Description of the Related Art
To drive a stepping motor, it is required to cause a phase of the motor to match with that of a phase signal, in other words, to perform a so-called “phase matching operation”, to prevent being out of phase. Conventionally, several phase matching methods have been proposed.
A method of energizing a stepping motor for a predetermined time at power-on of the motor has been proposed (see, for example, Japanese Patent Application Laid-Open No. 2001-292597). According to this method, the motor is energized again for a predetermined time when there is a possibility of being out of phase.
Another method of driving a stepping motor for drive pulses and for at least a first pulse after the motor is de-energized has been proposed (for example, see Japanese Patent Application Laid-Open No. 2001-346399). The at least first pulse drives the stepping motor to return to a position at which the motor is stopped before de-energization.
However, when a phase matching operation is performed immediately before the motor is started, a duration that elapses until the motor starts a main driving operation becomes longer. Consequently, the motor can fail to start driving in time when quick start-up is required of the motor. The phase matching operation referred to here means to drive a stepping motor by a small degree to thereby attain phase matching. In a broad sense, the phase matching operation is also a kind of a driving operation of the motor. Hence, in the following description, a driving operation a stepping motor performed for an intended purpose is referred to as “main driving operation” as in the above to distinguish the main driving operation from the phase matching operation.
Performing the phase matching operation at power-on or when a door is closed allows to spare the above-described inconvenience, however, there are some cases that phase matching cannot be attained only by energizing the motor for a predetermined time (a rotor remains to be out of phase and does not work).